Dispersing apparatus

ABSTRACT

It is an object to provide a continuous type dispersing apparatus arranged to disperse particle media in a vessel by stirring blades thereof to satisfactorily perform a process for dispersing a material to be dispersed to effectively use energy of the stirring blades to disperse pigment so as to reduce required quantity of the particle media to be discharged, prevent generation of short pass and chocking phenomena, secure safety, obtain excellent crushing efficiency and dispersing efficiency and attain economical advantage. The dispersing apparatus has a structure having first and second rotational shafts (5A, 5B) disposed in a vessel (3) having ports for supplying and discharging a material to be dispersed, to run parallel to each other and rotatively, a plurality of stirring blades (7A, 7B) provided in an axial direction and apart from one another at arbitrary intervals for the first and second rotational shafts and located alternately in the axial direction, and particle media arranged to perform a process for dispersing the material and enclosed in the vessel (3), wherein portions of rotational regions of the stirring blades (7A, 7B) provided for the first and second rotational shafts overlap, and the vessel (3) has an inner surface formed by combining two circular arc curved surfaces (9A, 9B) formed along the outer rotational ends of the stirring blades (7A, 7B) provided for the first and second rotational shafts.

TECHNICAL FIELD

The present invention relates to a dispersing apparatus for performing aprocess for dispersing a material, which is a raw material of a millbase, in which, for example, powder pigment is dispersed in a varnish ora solvent at a high concentration, and more particularly to a dispersingapparatus in which the distance for which the material to be dispersedis moved in a vessel thereof is elongated so as to sufficiently dispersethe material.

BACKGROUND ART

For example, ink for printing and a coating material have beenmanufactured by using a mill base in which powder pigment is dispersedin a varnish or a solvent at a high concentration. It is preferable thata process in which powder pigment is dispersed in a solvent or the likebe performed such that powder pigment of secondary particles in a statewhere primary particles of the pigment have been aggregated are crushedand dispersed in a solvent to form fine pigment particles in whichcoarse particles do not exist in order to improve the coloring power ofthe ink for printing or the coating material.

Hitherto, as the dispersing apparatus, a sand mill, a grain mill, a ballmill, an attritor and the like have been known. Among the dispersingapparatuses above, a structure for continuously performing thedispersing process and arranged as shown in FIG. 7 has been known.

That is, the structure is a horizontal structure having a cylindricalvessel 101 disposed horizontally. In the vessel 101, a rotational shaft103 is horizontally and rotatively disposed. A plurality of pin typestirring blades 105 projecting in the radial directions are provided forthe rotational shaft 103 to be disposed apart from one another atarbitrary intervals in the axial direction. In the vessel 101, sphericalparticle media 107 made of, for example, steel, ceramics or stones, areenclosed in order to perform the process for dispersing the material.

With the foregoing structure, when the rotational shaft 103 is rotatedby a motor or the like and a raw material for a mill base is suppliedthrough a supply port 109 formed at an end of the vessel 101, theparticle media 107 are stirred by the plurality of stirring blades 105provided for the rotational shaft 103. Therefore, the process fordispersing the raw material for the mill base can be performed. The millbase, subjected to the dispersing process, is continuously dischargedthrough a discharge port 111 formed at another end of the vessel 101.

The foregoing structure sometimes encounters a so-called short pass inwhich the raw material for the mill base supplied into the vessel 101through the supply port 109 cannot uniformly be dispersed and thereforethe mill base containing coarse pigment particles is discharged throughthe discharge port 111. Therefore, there arises a problem in that thedispersing process cannot satisfactorily be performed.

When the movement of the particle media 107 is observed, the particlemedia 107 are in a tendency to follow the rotation of the stirringblades 105 provided for the rotational shaft 103 and rotate togetherwith the same. Therefore, there arises a problem in that the dispersingprocess cannot effectively be performed.

If the rate of charging the particle media 107 into the vessel 101 israised in order to prevent the short pass, the short pass can somewhatbe prevented. If the rate of charging the particle media 107 Is raisedexcessively, a choking phenomenon takes place in which the particlemedia 107 are, in the J101, moved eccentrically toward the dischargeport 111. Thus, another problem arises in that the operation cannot beperformed safely. Accordingly, the rate of charging of the particlemedia is generally determined to be 75 to 80% at the time of performingthe operation.

A conventional structure shown in FIG. 8 can be available. The structureis a vertical structure in which a cylindrical vessel 101 is disposedvertically. A rotational shaft 103 having stirring blades 105 isvertically and rotatively disposed.

The foregoing structure is formed by converting the horizontal structureinto a vertical structure in which the raw material for the mill base issupplied into the vessel 101 through a supply port 109 opened and formedin the upper portion of the vessel 101. Moreover, the rotational shaft103 is rotated to stir the particle media 107 so that the process fordispersing the raw material for the mill base is performed. The millbase subjected to the dispersing process is discharged through thedischarge port 111 formed in the lower portion of the vessel 101. Thedischarge port 111 has a particle-media separation mechanism 113 in theform of, for example, a lattice or a net and arranged to preventdischarge of the particle media 107 and a raw-material discharge valve115 capable of opening/closing the discharge port 111.

Since the foregoing structure is formed by simply converting the vessel101 from the horizontal structure into the vertical structure, a problemsimilar to that suffered with the horizontal structure arises.

Another conventional structure is arranged as shown in FIGS. 9 and 10.Schematically, the foregoing structure is arranged such that first andsecond rotational shafts 117A and 117B are vertically disposed in avertical and cylindrical vessel 101. Plate-like first and secondstirring blades 119A and 119B having phases shifted from each other by90° are provided for the first and second rotational shafts 117A and117B so as to perform rotation while preventing interference of thefirst and second stirring blades 119A and 119B.

With the foregoing structure, portions of the loci of rotations of thefirst and second stirring blades 119A and 119B overlap. However, sinceeach of the first and second stirring blades 119A and 119B has aplate-like shape, a portion of the raw material for the mill base isrotated together in the vessel 101. Moreover, portions adjacent toregions 121A and 121B are outside the rotational regions for the firstand second stirring blades 119A and 119B. Thus, there arises a problemin that the process for dispersing the raw material for the mill basecannot satisfactorily be performed and the same is made to benon-uniform.

As prior arts considered to be related to the present invention, thereare inventions disclosed in Japanese Patent Laid-Open No. 1-224057(Prior Art 1), U.S. Pat. No. 4,673,134 (Prior Art 2), U.S. Pat. No.3,199,792 (Prior Art 3), U.S. Pat No. 4,919,347 (Prior Art 4), and U.S.Pat. No. 4,998,678 (Prior Art 5).

The Prior Art 1 has a structure such that first and second rotationalshafts are vertically and rotatively disposed in a vessel having anoblong cross sectional shape; and portions of rotation loci of the firstand second stirring blades provided for the first and second rotationalshafts overlap. However, dead spaces each having a substantially atriangular shape surrounded by the inner surface of the vessel and therotational loci are formed in front and rear of the portion in which theloci of rotations of the first and second stirring blades overlap and onthe two sides of the same when viewed in the rotational direction of thefirst and second stirring blades. The raw material for the mill baselocated in the dead spaces cannot satisfactorily be dispersed and thesame can easily be made non-uniform.

The Prior Art 2 has disclosed a structure such that stirring blades areprovided for a plurality of rotational shafts. Also the structure of thePrior Art 2 encounters the generation of the substantially triangulardead space between the rotation loci of the stirring blades and theinner surface of the vessel. Thus, a problem similar to that experiencewith the Prior Art 1 arises.

FIG. 8 of Prior Art 3 discloses a structure in which first and secondrotational shafts are vertically and rotatively disposed in a vesselhaving a shape formed by combining two circular arc curved planes; andstirring blades extending in three directions are provided for the firstand second rotational shafts. Each of the three stirring blades has aplate-like shape and arranged to be orated in opposite directions.Moreover, their rotation loci are in contact with each other. Althoughthe problem of the dead space can therefore be overcome, the particlemedia and the like are in a tendency of easily rotating together withthe stirring blades. Thus, there arises a problem in that the rawmaterial for the mill base cannot satisfactorily be dispersed.

The Prior Art 4 has disclosed a structure in which cylindrical first andsecond rotors each having a multiplicity of projections and pits on theouter surfaces thereof are disposed in a vessel having a shape formed bycombining two circular arc curved planes. The foregoing structure has aproblem in that the outer surface of the first rotor is not engaged withthe outer surface of the second rotor, therefore the rotation loci ofthe rotors do not overlap, and that the process for manufacturing therotor becomes too complicated.

The Prior Art 5 has disclosed a structure such that a rotational shaftis vertically and rotatively disposed at an eccentric position in arotative, vertical and cylindrical vessel. Moreover, a plurality ofdiscs having a plurality of holes in the vicinity of the outer endsthereof are provided for the rotational shaft. Since the foregoingstructure is arranged such that the vessel is rotated and the rotationalshaft disposed at an eccentric position in the vessel is rotated, therearises a problem in that the overall structure becomes too complicated.

DISCLOSURE OF INVENTION

The present invention has been established in view of theabove-mentioned problems. According to the invention, there is provideda dispersing apparatus comprising first and second rotational shaftsdisposed, in a vessel having ports for supplying and discharging amaterial to be dispersed, to run parallel to each other and rotatively,a plurality of stirring blades provided, in an axial direction and apartfrom one another at arbitrary intervals, for the first and secondrotational shafts and located alternately in the axial direction, andparticle media arranged to perform a process for dispersing the materialand enclosed in the vessel, wherein portions of rotational regions ofthe stirring blades provided for the first and second rotational shaftsoverlap, and the vessel has an inner surface formed by combining twocircular arc curved surfaces formed along the outer rotational ends ofthe stirring blades provided for the first and second rotational shafts.

As a result of the above-mentioned structure, when the first and secondrotational shafts are rotated and the material to be dispersed aresupplied through the supply portion of the vessel, the particle mediaare, in the vessel, stirred by the stirring blades so that the materialto be dispersed is subjected to the dispersing process. Since the innersurface of the vessel is formed by combining two circular arc curvedplane formed along the rotational end of the stirring blades providedfor the first and second rotational shafts and portions of therotational regions of the stirring blades overlap, dead space in whichthe particle media cannot satisfactorily be stirred is not formed in thevessel. Moreover, since the rotational direction of the first and secondrotational shafts are made to be the same, the directions in which thestirring blades are moved in opposite directions in the region in whichthe rotational regions of the stirring blades overlap. Therefore, mutualcollision of the particle media causing the same to be rotate togethercan be prevented. In case the rotational direction of the first andsecond rotational shafts made to be opposite, mutual collision of theparticle media causing the same to be rotate together can be disturbedin the region in which the rotational regions of the stirring bladesoverlap. Therefore, the rotational direction of the first and secondrotational shafts are not limited to the same, it is preferable thatthey are the same.

Therefore, the material to be dispersed can satisfactorily be dispersedin the region in which the rotational regions overlap. Therefore,pigment particles in the solvent can furthermore be fined and differencein the concentration can be eliminated and the pigment particles can bemade to be uniform.

The invention has a structure such that the first and second rotationalshafts are disposed horizontally, and a plane including the axes of thefirst and second rotational shafts is a vertical plane. Therefore, thestructure is formed such that the first and second rotational shafts aredisposed vertically. Thus, the load of the particle media in the chamberin which the upper rotational shaft is disposed acts on the particlemedia in the chamber in which the lower rotational shaft is disposed.Moreover, the lower chamber is brought to a state where it is filledwith the particle media. Therefore, the dispersing process canfurthermore effectively be performed.

The invention has a structure such that the first and second rotationalshafts are disposed horizontally, and a plane including the axes of thefirst and second rotational shafts is a horizontal plane. Therefore, thefirst and second rotational shafts are disposed adjacently in ahorizontal direction. As a result, the quantities of the particle mediain the chambers in which the first and second rotational shafts aredisposed are made to be substantially the same and the material to bedispersed can easily be allowed to meander in each chamber. Thus, thedistance for which the material to be dispersed is moved from the supplyport to the discharge port can be lengthened and the dispersing processcan sufficiently be performed.

The invention has a structure such that the first and second rotationalshafts are disposed horizontally, and a plane including the axes of thefirst and second rotational shafts can be changed between a verticalstate and a horizontal state. Therefore, the positional relationshipbetween the first and second rotational shafts can be varied in thevertical state and the horizontal state. As a result, thecharacteristics of both of the states are used to effectively performthe dispersing process.

The invention has a structure such that the first and second rotationalshafts are disposed vertically and a plane including the axes of thefirst and second rotational shafts is a vertical plane. Therefore, thechambers in which the first and second rotational shafts are disposedare vertically disposed so that the quantities of the particle media inthe chambers in which the first and second rotational shafts aredisposed are made to be substantially the same and the material to bedispersed are easily be allowed to meander in each chamber. As a result,an effect similar to that obtainable from the invention.

The invention has a structure such that at least one plate-like blade isprovided for at least either of the first and second rotational shafts.Therefore, the plate-like blade realizes a tendency of preventingmovement of the material to be dispersed along the shaft so thatmeandering of the material to be dispersed is enhanced. As a result,meandering can be performed effectively and the distance for which thematerial to be dispersed is moved can be lengthened. As a result, thedispersing process can effectively be performed.

The invention has a structure such that assuming that radii of the firstand second rotational shafts are rA and rB, rotational radii of each ofthe stirring blades provided for the first and second rotational shaftsare RA and RB, and distance between axes of the first and secondrotational shafts is L, a relationship rB+RA=rA+RB<L≦0.9 (RA+RB) issatisfied. Therefore, portions of the rotational regions of the stirringblades provided for the first and second rotational shafts alwaysoverlap. Thus, rotations of the particle media together with thestirring blades can be prevented in the overlap portion.

The invention has a structure such that the distance from the outersurface of each of the first and second rotational shafts and therotational outer ends of the stirring blades provided for the first andsecond rotational shafts and the distance from the rotational outer endsof the stirring blades and the inner surface of the vessel are not lessthan three times the mean diameter of the particle media nor more thanabout 10 times. Therefore, clogging of the particle media in the gapsbetween the first and second rotational shafts and stirring blades andbetween the stirring blades and the inner surface of the vessel can beprevented. Moreover, deterioration in the dispersing processattributable to the excessively large gap can be prevented.

The invention has a structure such that the rotational directions of thefirst and second rotational shafts are the same. Therefore, thedirection in which the stirring blades are moved are made to be oppositein the position at which the rotational regions of the stirring bladesoverlap. As a result, rotations of the particle media together with therotational shafts can effectively be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of explanation schematically showing adispersing apparatus according to a first embodiment of the presentinvention;

FIG. 2 is a cross sectional view of explanation taken along line 2--2shown in FIG. 1;

FIG. 3 is a cross sectional view of explanation showing a dispersingapparatus according to a second embodiment of the present invention;

FIG. 4 is a cross sectional view of explanation taken along line 4--4shown in FIG. 3;

FIG. 5 is a cross sectional view of explanation schematically showing adispersing apparatus according to a third embodiment of the presentinvention;

FIG. 6A-E, C', D' is a schematic and conceptual view showing dispersingapparatuses according to a comparative example and the presentinvention;

FIG. 7 is a cross sectional view of explanation schematically showing adispersing apparatus according to a first example of a conventionalapparatus;

FIG. 8 is a cross sectional view of explanation schematically showing adispersing apparatus according to a second example of the conventionalapparatus;

FIG. 9 is a cross sectional view of explanation schematically showing adispersing apparatus according to a third example of the conventionalapparatus; and

FIG. 10 is a plain cross sectional view of FIG. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the drawings.

Referring to FIGS. 1 and 2, a dispersing apparatus 1 according to afirst embodiment has a cylindrical vessel 3 having a horizontal axis.The vessel 3 includes first and second rotational shafts 5A and 5Brunning in parallel to each other and disposed horizontally androtatively. The first and second rotational shafts 5A and 5B have aplurality of pin-shape stirring blades 7A and 7B projecting andelongating in a radial direction and disposed at arbitrary intervals inthe axial direction.

More specifically, the inner surface of the foregoing vessel 3, as shownin FIG. 2, is formed into a shape realized by joining circular-arccurved surfaces 9A and 9B formed along the outer surfaces of therotating stirring blades 7A and 7B provided for the first and secondrotational shafts 5A and 5B. That is, the cross sectional shape in whichthe first and second rotational shafts 5A and 5B are disposed is formedinto a shape realized by joining first and second chambers 11A and 11Beach having a substantially 3/4 circular arc shape, the shape being in asupercilium shape.

The vessel 3 has an outer wall 13 on the outside of an inner wall havingthe circular-arc curved surfaces 9A and 9B. A cooling chamber 15Ccommunicated with an inlet port 15A and an outlet port 15B for a coolingmedium is formed between the inner wall and the outer wall 13. A firstcover member 19, having a supply port 17 for a raw material for the millbase in which, for example, powder pigment has been dispersed in avarnish or a solvent at a high concentration, is detachably secured toan end of the vessel 3 by arbitrary fixing members (not shown), such asbolts.

At another end of the vessel 3, there is, by arbitrary fixing members,detachably attached a second cover member 21 horizontally and rotativelysupporting the first and second rotational shafts 5A and 5B. The secondcover member 21 has a discharge port 23. Between the second cover member21 and the vessel 3, there is disposed a net or a lattice shapeparticle-media separation mechanism 27 in order to disperse a particlemedia 25 filled in the vessel 3 and the material to be dispersed (themill base) subjected to the dispersing process.

The particle media 25 is, for example, spherical, flat or amorphoussteel, ceramics, crystal or the like. In the case where the sphericalmedia is employed, a media having a mean particle size of 0.2 mm to 15mm is employed. The charging rate of the particle media 25 in the vessel3 is 70 to 95%.

Although the first and second rotational shafts 5A and 5B have coolingmedium passage through which the cooling medium can be circulated, thecooling medium passage are not always necessary. Each of the stirringblades 7A and 7B provided for the first and second rotational shafts 5Aand 5B according to this embodiment is in the form of a projectingcruciform consisting of four pins disposed in the radial direction. Thenumber of the pins is not limited to four but the number may be anarbitrary number. The cross sectional shape of each pin is not limitedto the circular shape but it may be another arbitrary shape.

The stirring blades 7A and 7B provided for the first and secondrotational shafts 5A and 5B are, as shown in FIG. 1, are alternatelydisposed in the axial direction of each of the first and secondrotational shafts 5A and 5B. Moreover, rotation regions 29A and 29B ofthe stirring blades 7A and 7B are, as shown in FIG. 2, structured suchthat their portions overlap.

The first and second rotational shafts 5A and 5B are arranged to berotated at the same speed in the same direction by a motor (not shown).At this time, it is preferable that the circumferential speed of each ofthe stirring blades 7A and 7B be 6 m/s to 17 m/s and the twocircumferential speeds are the same.

Assuming that the radii of the first and second rotational shafts 5A and5B of the above-mentioned structure respectively are rA and rB, therotational radii of the stirring blades 7A and 7B respectively are RAand RB, and the distance between the first and second rotational shafts5A and 5B is L, a relationship rB+RA=rA+RB<L≦0.9 (RA+RB) is held. Thedistance from the surface of each of the first and second rotationalshafts 5A and 5B and the outer surface of each of the stirring blades 7Band 7A at the time of the rotation and the distance from the outersurface of each of the stirring blades 7A and 7B at the time of therotation and the inner surface of the vessel 3 is not less than threetimes the mean diameter of the particle media 25 nor more than about 10times of the same.

Therefore, the particle media 25 cannot be interposed between thestirring blades 7A and 7B and the first and second rotational shafts 5Aand 5B and the inner surfaces 9A and 9B of the first and second chambers11A and 11B. Moreover, a problem of a type which arises in that thestirring efficiency and the like deteriorate attributable to anexcessively long distance between the stirring blades 7A and 7B and theinner surfaces 9A and 9B can be prevented.

In the structure above, when the first and second rotational shafts 5Aand 5B are rotated in the same directions and the raw material for themill base (material to be dispersed) is supplied into the vessel 3 fromthe supply port 17, the particle media 25 in the vessel 3 are moved andstirred by the plural stirring blades 7A and 7B provided for the firstand second rotational shafts 5A and 5B. Thus, the material to bedispersed is brought to a state where it is mixed with the particlemedia 25 and stirred so that the dispersing process is performed.

At this time, the material to be dispersed alternately meanders in thefirst and second chambers 11A and 11B in which the first and secondrotational shafts 5A and 5B are disposed attributable to rotations ofthe stirring blades 7A and 7B. Therefore, the distance of the movementis lengthened. As a result of the rotations of the stirring blades 7Aand 7B, the particle media 25 in the vessel 3 are in a trend offollowing the rotations of the stirring blades 7A and 7B and thereforerotating together with the same. In the portion in which the rotationregions 29A and 29B of the stirring blades 7A and 7B overlap, theparticle media 25 collide with one another because the directions of themovement of the stirring blades 7A and 7B are opposite to each other. Asa result, the collective rotation can effectively be prevented.Moreover, the collision enables stirring to be performed effectively. Asa result, the material to be dispersed can be dispersed more effectivelyin the overlap portion.

The material to be dispersed, which has been subjected to the dispersingprocess, is separated from the particle media 25 by a particle-mediaseparation mechanism 27, and then discharged to the outside through thedischarge port 23.

As can be understood from the description above, the material to bedispersed alternately meanders in the first and second chambers 11A and11B, thus causing the distance of movement to be lengthened. Moreover, aphenomenon that the material to be dispersed collides with the particlemedia 25 in the region in which the rotational regions of the stirringblades 7A and 7B overlap. As a result, stirring can effectively beperformed, thus enabling the amount of the particle media 25, which mustcharged, to be reduced.

In order to confirm the effect of the dispersing apparatus having theforegoing structure, a comparison test was performed.

EXAMPLES Example 1 to 7 and Comparative Examples 1 to 7

Pigment (12 parts by weight), alkyd resin (38 parts by weight) andxylene (40 parts by weight) were mixed with the foregoing ratio, andthen the mixed material was dispersed in a dispersing apparatus havingthe structure as shown in FIGS. 1 and 2 and according to the presentinvention. As a result, a pigment dispersed base was prepared. Melamineresin (12 parts by weight) was mixed with the pigment dispersed base (88parts by weight) so that an alkyd/melamine coating material wasprepared. As comparative examples, coating materials were employed whichwere obtained by, for the same time, dispersing raw materialsrespectively having the same compositions as those of the materialsaccording to examples by using a conventional uniaxial sand millstructured as shown in FIG. 7. The particle size distribution wasmeasured, thus resulting in the pigments obtained by using thedispersing apparatus according to the present invention had smallerparticle sizes as compared with the pigments obtained by the dispersingapparatus according to the comparative examples as shown in Table 1. Asa result, excellent dispersing characteristic was exhibited.

The foregoing coating material was diluted by a base coating material oftitanium oxide (which was paste, in which titanium oxide was dispersedand which was obtained by dispersing titanium oxide in an alkyd/melaminesystem with 50 PHR) in such a manner that the ratio of the pigment andtitanium oxide was 1/10 so that light-color coating material wasprepared. The light color coating material was applied to art paper by a6 mm applicator, and then allowed to stand for 10 minutes. Then, thecoloring power of each coated film baked at 140° C. for 30 minutes wasmeasured. The color power coloring power was obtained in accordance withcolor difference value DL measured such that the comparative example wasemployed as a reference such that the color power was expressed by(100-DL×10) assuming that the coloring power of the comparative examplewas made to be 100. As shown in Table 1, the coated films formed byusing the dispersing apparatus according to the present inventionexhibited stronger coloring power than that formed by using thedispersing apparatus according to the comparative examples.

The viscosity of each coating materials was adjusted such that 20seconds are realized in a #4 Ford cup, and then the coating material wasapplied to an intercoated plate (a steel plate previously applied with aprimer coating material and then wet-rubbed) to have a dry filmthickness of about 30 mm by using an air spray and then allowed to standfor 10 minutes. Then, the coated film was baked at 140° C. for 30minutes. The luster of the coated plate was measured, thus resulting inthat the coated plate formed by using the dispersing apparatus accordingto the present invention exhibited excellent luster of the coated filmas compared-with the luster of the coated plate formed by using thedispersing apparatus according to the comparative example, as shown inTable 1.

                  TABLE 1                                                         ______________________________________                                                                       Luster                                                       article Size     (%)                                                                Distribution                                                                            Coloring                                                                             20°                                                                         60°                          Examples                                                                              Pigment     D50 (μm)                                                                             Power  G    G                                   ______________________________________                                        Comparative                                                                           C.I.Pigment Red                                                                           0.20      100    45.8 75.5                                Example 1                                                                             177                                                                   Example 1                                                                             (Anthraquinoe                                                                             0.12      110    77.9 85.4                                        Pigment)                                                              Comparative                                                                           C.I.Pigment 0.32      100    55.4 78.8                                Example 2                                                                             Violet 19                                                             Example 2                                                                             (Quinacridon                                                                              0.22      115    80.6 88.4                                        Pigment)                                                              Comparative                                                                           C.I.Pigment Red                                                                           0.27      100    60.9 79.5                                Example 3                                                                             178                                                                   Example 3                                                                             (Perylene   0.19      112    82.0 89.8                                        Pigment)                                                              Comparative                                                                           C.I.Pigment Blue                                                                          0.31      100    61.4 80.3                                Example 4                                                                             15:1                                                                  Example 4                                                                             (Pthalocyanine                                                                            0.24      118    83.5 91.5                                        Pigment)                                                              Comparative                                                                           C.I.Pigment 0.25      100    60.5 79.1                                Example 5                                                                             Violet 23                                                             Example 5                                                                             (Dioxazine  0.18      108    81.1 88.0                                        Pigment)                                                              Comparative                                                                           C.I.Pigment Red                                                                           0.36      100    54.0 76.5                                Example 6                                                                             254                                                                   Example 6                                                                             (Diketopyroropyr                                                                          0.25      112    79.5 85.9                                        role Pigment)                                                         Comparative                                                                           C.I.Pigment Red                                                                           0.20      100    70.3 85.2                                Example 7                                                                             101                                                                   Example 7                                                                             (Inorganic  0.11      110    80.7 93.0                                        Pigment)                                                              ______________________________________                                         Luster: luster level at changed angles of 20° and 60              

In a case where a comparison was made by using dispersing apparatushaving the same capacities, the performance for manufacturing theprinting ink mill base was improved by about 50%.

FIGS. 3 and 4 show a dispersing apparatus 1A according to a secondembodiment. The dispersing apparatus 1A has a vessel 3A having the samecross sectional shape as that of the vessel 3 according to the firstembodiment and disposed vertically. A supply port 17A is formed in theupper portion of the vessel 3A. Moreover, a discharge port 111, aparticle-media separation mechanism 113 and a valve 115 respectivelyhaving the structures similar to those of the conventional structure aredisposed in the bottom portion. Since the other structures aresubstantially the same as those according to the first embodiment,elements having the same functions are given the same reference numeralsand the similar portions are omitted from illustration.

In the second embodiment, the axis of the vessel 3 and the first andsecond rotational shafts 5A and 5B are perpendicular to each other.Moreover, a plane including the axis of the first and second rotationalshafts 5A and 5B is made vertical. Therefore, the first and secondchambers 11A and 11B in which the first and second rotational shafts 5Aand 5B are located are formed adjacently in the horizontal direction. Asa result, the quantity of the particle media in the first and secondchambers 11A and 11B are substantially the same. The material to bedispersed, which has been supplied into the vessel 3A through the supplyport 17A, meanders in each of the first and second chambers 11A and 11Bto reach the discharge port 111. As a result, a similar effect to thatobtainable from the first embodiment can be obtained.

In order to confirm the effects of the dispersing apparatus according tothe second embodiment, a comparison test was performed.

EXAMPLES Examples 1 to 7 and Comparative Examples 1 to 7

Pigment (12 parts by weight), alkyd resin (38 parts by weight) andxylene (40 parts by weight) were mixed with the foregoing ratio, andthen the mixed material was dispersed in a dispersing apparatus havingthe structure as shown in FIGS. 3 and 4 and according to the presentinvention. As a result, a pigment dispersed base was prepared. Melamineresin (12 parts by weight) was mixed with the pigment dispersed base (88parts by weight) so that an alkyd/melamine coating material wasprepared. As comparative examples, coating materials were employed whichwere obtained by, for the same time, dispersing raw materialsrespectively having the same compositions as those of the materialsaccording to examples by using a conventional uniaxial sand millstructured as shown in FIG. 8. The particle size distribution wasmeasured, thus resulting in the pigments obtained by using thedispersing apparatus according to the present invention had smallerparticle sizes as compared with the pigments obtained by the dispersingapparatus according to the comparative examples as shown in Table 2. Asa result, excellent dispersing characteristic was exhibited.

                  TABLE 2                                                         ______________________________________                                                                article Size                                                                  Distribution                                                                             Coloring                                   Examples Pigment        D50 (μ) Power                                      ______________________________________                                        Comparative                                                                            C.I.Pigment Red 177                                                                          0.25       100                                        Example 1                                                                     Example 1                                                                              (Anthraquinoe Pigment)                                                                       0.20       107                                        Comparative                                                                            C.I.Pigment Violet 19                                                                        0.37       100                                        Example 2                                                                     Example 2                                                                              (Quinacridon Pigment)                                                                        0.27       112                                        Comparative                                                                            C.I.Pigment Red 176                                                                          0.31       100                                        Example 3                                                                     Example 3                                                                              (Perylene Pigment)                                                                           0.23       108                                        Comparative                                                                            C.I.Pigment Blue 15:1                                                                        0.36       100                                        Example 4                                                                     Example 4                                                                              (Pthalocyanine 0.28       115                                                 Pigment)                                                             Comparative                                                                            C.I.Pigment Violet 23                                                                        0.30       100                                        Example 5                                                                     Example 5                                                                              (Dioxazine Pigment)                                                                          0.24       106                                        Comparative                                                                            C.I.Pigment Red 254                                                                          0.39       100                                        Example 6                                                                     Example 6                                                                              (Diketopyroropyrrole                                                                         0.29       110                                                 Pigment)                                                             Comparative                                                                            C.I.Pigment Red 101                                                                          0.25       100                                        Example 7                                                                     Example 7                                                                              (Inorganic Pigment)                                                                          0.17       108                                        ______________________________________                                    

The foregoing coating material was diluted by a base coating material oftitanium oxide (which was paste, in which titanium oxide was dispersedand which was obtained by dispersing titanium oxide in an alkyd/melaminesystem with 50 PHR) in such a manner that the ratio of the pigment andtitanium oxide was 1/10 so that light-color coating material wasprepared. The light color coating material was applied to art paper by a6 mm applicator, and then allowed to stand for 10 minutes. Then, thecoloring power of each coated film baked at 140° C. for 30 minutes wasmeasured. The color power coloring power was obtained in accordance withcolor difference value DL measured such that the comparative example wasemployed as a reference such that the color power was expressed by(100-DL×10) assuming that the coloring power of the comparative examplewas made to be 100. As shown in Table 1, the coated films formed byusing the dispersing apparatus according to the present inventionexhibited stronger coloring power than that formed by using thedispersing apparatus according to the comparative examples.

In a case where a comparison was made by using dispersing apparatushaving the same capacities, the performance for manufacturing theprinting ink mill base was improved by about 50%.

The dispersing apparatus 1 shown in FIGS. 1 and 2 has the structure suchthat a plane including the axes of the first and second rotationalshafts 5A and 5B is horizontal and the first and second chambers 11A and11B in which the first and second rotational shafts 5A and 5B arelocated are disposed horizontally. Another structure may be employed inwhich the plane including the axes of the first and second rotationalshafts 5A and 5B are made to be vertical. That is, the first and secondchambers 11A and 11B in which the first and second rotational shafts 5Aand 5B are located may be disposed vertically.

With the structure above, the lower chamber in the vessel is filled withthe particle media and the weight of the particle media acts on theparticle media in the lower chamber so that the dispersing process canbe performed more efficiently in the lower chamber.

As can be understood from the foregoing description, the plane includingthe first and second rotational shafts 5A and 5B can be disposedhorizontally or vertically. Therefore, employment of a structure inwhich the body of the vessel can be rotated around the horizontal axisthereof enables the plane including the axes of the first and secondrotational shafts 5A and 5B to be changed between the horizontal stateand the vertical state. The vertical relationship between the first andsecond chambers 11A and 11B in the vessel can be disposed conversely.

In the foregoing case, the positional relationship between the first andsecond chambers 11A and 11B in the vessel can be changed betweenhorizontal and vertical positions. Therefore, the dispersing process canbe performed by using the characteristics of both of the structures inwhich the first and second chambers 11A and 11B are formed horizontallyand in which the same are formed vertically.

FIG. 5 shows a third embodiment. The third embodiment has substantiallythe same structure according to the first embodiment shown in FIGS. 1and 2. The difference lies in that discs 31A and 31B disposed at anarbitrary distance respectively are provided for the first and secondrotational shafts 5A and 5B so that short pass is prevented in which thematerial to be dispersed supplied into the vessel through the supplyport 17 is moved in a direction along the first and second rotationalshafts 5A and 5B. Moreover, the tendency in which the material to bedispersed meanders in the first and second chambers 11A and 11B can beenhanced. Since the other structures are the same as those according tothe first embodiment, the components having the same functions are giventhe same reference numerals and the repeated description is omitted.

With the foregoing structure, the material to be dispersed supplied intothe vessel 3 through the supply port 17 is reliably inhibited from beinglinearly movement toward the discharge port 23 by the discs 31A and 31B.Since the material to be dispersed reaches the discharge port 23 whilemeandering in the first and second chambers 11A and 11B, the distancefor which the material to be dispersed is moved can be lengthened.Therefore, a further effective dispersing process can be performed.

As can be understood from the description above, the structure shown inFIG. 5 may be arranged such that the positional relationship between thefirst and second rotational shafts 5A and 5B has a verticalrelationship. Also the structure shown in FIG. 3 may be formed such thatthe discs 31A and 31B are provided for the first and second rotationalshafts 5A and 5B.

Results of experiments performed by using the dispersing apparatusesrespectively having structures (A) and (B) according to the comparativeexamples and those (C), (C'), (D), (D') and (E) according to the presentinvention and as shown schematically in FIG. 6 are shown in Table 3. Afact was confirmed that the dispersing apparatuses according to thepresent invention have satisfactorily performed the dispersing process.

Note that symbols indicating the type of the dispersing apparatuses (A),(B), (C), (D), (E), (C') and (D') shown in Table 3 indicate thedispersing apparatuses schematically shown in FIG. 6.

In FIG. 6, the type (A) corresponds to the structure shown in FIG. 7.The type (B) has a structure such that the first and second rotationalshafts 5A and 5B are disposed in a horizontal and cylindrical vessel andthe rotational regions of the stirring blades 7A and 7B provided for thefirst and second rotational shaft do not overlap. The types (A) and (B)are structures according to the comparative examples.

The type (C) shown in FIG. 6 has a structure corresponding to thedispersing apparatus structured as shown in FIGS. 1 and 2. The type (D)corresponds to the structure formed by rotating the structure of thetype (C) by 90°. The type (E) corresponds to the dispersing apparatushaving the structure shown in FIGS. 3 and 4. The type (C') correspondsto the dispersing apparatus shown in FIG. 5 and has a structure suchthat the disc is provided for the type (C). The type (D') corresponds toa structure such that the structure of the type (C') is rotated by 90°and a disc is provided for the type (D).

                  TABLE 3                                                         ______________________________________                                        Type of               Particle                                                Dis-                  Size           Luster                                   persing               Distribut                                                                              Color-                                                                              (%)                                              Appa-             ion    ing   20°                                                                         60°                        Examples                                                                              ratuses Pigment   D50 (μm)                                                                          Power G    G                                 ______________________________________                                        Comparative                                                                           (A)               0.31   100   61.4 80.3                              Example 1                                                                     Comparative                                                                           (B)               0.30   102   63.0 85.0                              Example 2                                                                     Example 1                                                                             (C)               0.24   118   83.5 91.5                              Example 2                                                                             (D)     C.I.Pigment                                                                             0.23   120   83.7 92.0                                              Blue                                                                          15:1                                                          Example 3                                                                             (E)     (Pthalocyani                                                                            0.28   115   81.0 86.5                                              ne Pigment)                                                   Example 3                                                                              (C')             0.21   120   84.3 92.0                              Example 4                                                                              (D')             0.20   121   84.5 92.3                              Comparative                                                                           (A)               0.32   100   55.4 78.8                              Example 1                                                                     Comparative                                                                           (B)     Quinacridon                                                                             0.30   103   57.0 79.5                              Example 3                                                                     Example 6                                                                             (C)     (Quinacridon                                                                            0.22   115   80.6 88.4                                              Pigment)                                                      Example 7                                                                             (D)               0.19   118   80.8 88.7                              ______________________________________                                    

Although the invention has been described in its preferred form, thepresent invention is not limited to the form of the embodiments aboveand the present disclosure of the preferred form can be changed.

That is, the foregoing embodiments have been described about thestructure in which the first and second rotational shafts are rotated inthe same directions. Although the first and second rotational shafts maybe rotated in opposite directions, it is preferable that they rotate inthe same direction. Another structure may be employed in which rotationsof the first and second rotational shafts in the same direction and thatin the opposite directions are repeated at every arbitrary time.

The structure shown in FIGS. 1 and 3 may be arranged such that acircular arc interrupting plate for preventing linear movement of thematerial to be dispersed along the inner surface of the vessel isprovided for an arbitrary range of the inner surface of the vessel suchthat the interruption plate slightly projects in the inner directionwhile preventing interruption of the stirring blades.

In place of the pin type stirring blades provided for the first andsecond rotational shafts, a plurality of disc type stirring blades maybe disposed. In the foregoing case, the disc type stirring blades mayhave a plurality of through holes each having an arbitrary size and ashape, or the through holes may be omitted. Moreover, the disc typestirring blades each having the through hole and disc type stirringblade having no through holes may be mixed.

In addition, the rotational radii of the first and second stirringblades provided for the first and second rotational shafts may be madeto be different.

INDUSTRIAL APPLICABILITY

As can be understood from the description of the embodiments, accordingto the invention claimed in claim 1, when the first and secondrotational shafts are rotated and the material to be dispersed issupplied through the supply port of the vessel, the particle media isstirred by the stirring blades so that the process for dispersing thematerial is performed. Since the inner surface of the vessel has a shapeformed by combining two circular arc curved planes formed along therotational end of each of the stirring blades provided for the first andsecond rotational shafts and the portions of the rotational regions ofthe stirring blades overlap, dead space, in which the particle mediacannot easily be stirred, is not generated in the vessel. Since therotational directions of the first and second rotational shafts are madeto be the same, the directions in which the stirring blades are movedare made to be opposite to each other in the region in which therotational region of the stirring blades overlap. Therefore, thecollision of the particle media and rotations of the same together withthe rotational shaft can be prevented.

As a result, the process for dispersing the material can effectively beperformed, pigment particles in the solvent can furthermore be fined,difference in the concentration can be eliminated and the pigmentparticles can be made to be uniform.

According to the invention claimed in claim 2, the load of the particlemedia in the chamber in which the upper rotational shaft is disposedacts on the particle media in the chamber in which the lower rotationalshaft is disposed. Moreover, the lower chamber is brought to a statewhere it is filled with the particle media. Therefore, a furthereffective dispersing process can be performed.

According to the invention claimed in claim 3, the quantities of theparticle media in the chambers in which the first and second rotationalshafts are disposed are made to be substantially the same and thematerial to be dispersed can easily be allowed to meander in eachchamber. Thus, the distance for which the material to be dispersed ismoved from the supply port to the discharge port can be lengthened andthe dispersing process can sufficiently be performed.

According to the invention claimed in claim 4, the positionalrelationship between the first and second rotational shafts can bevaried in the vertical state and the horizontal state. As a result, thecharacteristics of both of the states are used to effectively performthe dispersing process.

According to the invention claimed in claim 5, the chambers in which thefirst and second rotational shafts are disposed are vertically disposedso that the quantities of the particle media in the chambers in whichthe first and second rotational shafts are disposed are made to besubstantially the same and the material to be dispersed are easily beallowed to meander in each chamber. As a result, the distance for whichthe material to be dispersed is moved can be lengthened so that thesecondary particles is performed more effectively.

According to the invention claimed in claim 6, the plate-like bladerealizes a tendency of preventing movement of the material to bedispersed along the shaft so that meandering of the material to bedispersed is enhanced. As a result, meandering can be performedeffectively and the dispersing process can effectively be performed.

According to the invention claimed in claim 7, portions of therotational regions of the stirring blades provided for the first andsecond rotational shafts always overlap. Thus, rotations of the particlemedia together with the stirring blades can be prevented in the overlapportion.

According to the invention claimed in claim 8, clogging of the particlemedia in the gaps between the first and second rotational shafts andstirring blades and between the stirring blades and the inner surface ofthe vessel can be prevented. Moreover, deterioration in the dispersingprocess attributable to the excessively large gap can be prevented.

According to the invention claimed in claim 9, the direction in whichthe stirring blades are moved are made to be opposite in the position atwhich the rotational regions of the stirring blades overlap. As aresult, rotations of the particle media together with the rotationalshafts can effectively be prevented.

We claim:
 1. A dispersing apparatus comprising:a vessel having ports forsupplying and discharging a material to be dispersed; first and secondrotational shafts disposed in said vessel to run parallel to each otherand rotatively; a plurality of stirring blades provided, in an axialdirection and apart from one another at arbitrary intervals, for saidfirst and second rotational shafts and located alternately in the axialdirection; and particle media arranged to perform a process fordispersing said material and enclosed in said vessel; wherein: portionsof rotational regions of said stirring blades provided for said firstand second rotational shafts overlap, said vessel has an inner surfaceformed by combining two circular arc-curved surfaces formed along outerrotational ends of said stirring blades provided for said first andsecond rotational shafts, said first and second rotational shafts aredisposed horizontally, a vertical plane includes axes of said first andsecond rotational shafts, and assuming that radii of said first andsecond rotational shafts are rA and rB, rotational radii of each of saidstirring blades provided for said first and second rotational shafts areRA and RB, and a distance between axes of said first and secondrotational shafts is L, so that a relationship rB+RA=rA+RB<L≦0.9 (RA+RB)is satisfied.
 2. A dispersing apparatus according to claim 1, wherein atleast one plate-like blade is provided for at least either of said firstand second rotational shafts.
 3. A dispersing apparatus according toclaim 2, wherein a distance from an outer surface of each of said firstand second rotational shafts to the outer rotational outer ends of saidstirring blades provided for said first and second rotational shafts anda distance from the outer rotational ends of said stirring blades to theinner surface of said vessel are not less than three times a meandiameter of said particle media nor more than ten times.
 4. A dispersingapparatus according to claim 3, wherein rotational directions of saidfirst and second rotational shafts are the same.
 5. A dispersingapparatus according to claim 2, wherein rotational directions of saidfirst and second rotational shafts are the same.
 6. A dispersingapparatus comprising:a vessel having ports for supplying and discharginga material to be dispersed; first and second rotational shafts disposedin said vessel to run parallel to each other and rotatively; a pluralityof stirring blades provided, in an axial direction and apart from oneanother at arbitrary intervals, for said first and second rotationalshafts and located alternately in the axial direction; and particlemedia arranged to perform a process for dispersing said material andenclosed in said vessel; wherein:portions of rotational regions of saidstirring blades provided for said first and second rotational shaftsoverlap, said vessel has an inner surface formed by combining twocircular arc-curved surfaces formed along outer rotational ends of saidstirring blades provided for said first and second rotational shafts,said first and second rotational shafts are disposed horizontally, avertical plane includes axes of said first and second rotational shafts,and a distance from an outer surface of each of said first and secondrotational shafts to the outer rotational ends of said stirring bladesprovided for said first and second rotational shafts and a distance fromthe outer rotational ends of said stirring blades to the inner surfaceof said vessel are not less than three times a mean diameter of saidparticle media nor more than ten times.
 7. A dispersing apparatusaccording to claim 6, wherein at least one plate-like blade is providedfor at least either of said first and second rotational shafts.
 8. Adispersing apparatus according to claim 7, wherein rotational directionsof said first and second rotational shafts are the same.
 9. A dispersingapparatus comprising:a vessel having ports for supplying and discharginga material to be dispersed; first and second rotational shafts disposedin said vessel to run parallel to each other and rotatively; a pluralityof stirring blades provided, in an axial direction and apart from oneanother at arbitrary intervals, for said first and second rotationalshafts and located alternately in the axial direction; and particlemedia arranged to perform a process for dispersing said material andenclosed in said vessel; wherein:portions of rotational regions of saidstirring blades provided for said first and second rotational shaftsoverlap, said vessel has an inner surface formed by combining twocircular arc-curved surfaces formed along outer rotational ends of saidstirring blades provided for said first and second rotational shafts,said first and second rotational shafts are disposed horizontally, avertical plane includes axes of said first and second rotational shafts,and rotational directions of said first and second rotational shafts arethe same.
 10. A dispersing apparatus according to claim 9, wherein atleast one plate-like blade is provided for at least either of said firstand second rotational shafts.
 11. A dispersing apparatus comprising:avessel having ports for supplying and discharging a material to bedispersed; first and second rotational shafts disposed in said vessel torun parallel to each other and rotatively; a plurality of stirringblades provided, in an axial direction and apart from one another atarbitrary intervals, for said first and second rotational shafts andlocated alternately in the axial direction; and particle media arrangedto perform a process for dispersing said material and enclosed in saidvessel; wherein:portions of rotational regions of said stirring bladesprovided for said first and second rotational shafts overlap, saidvessel has an inner surface formed by combining two circular arc-curvedsurfaces formed along outer rotational ends of said stirring bladesprovided for said first and second rotational shafts, said first andsecond rotational shafts are disposed horizontally, a horizontal planeincludes axes of said first and second rotational shafts, and assumingthat radii of said first and second rotational shafts are rA and rB,rotational radii of each of said stirring blades provided for said firstand second rotational shafts are RA and RB, and a distance between axesof said first and second rotational shafts is L, so that a relationshiprB+RA=rA+RB<L≦0.9 (RA+RB) is satisfied.
 12. A dispersing apparatusaccording to claim 11, wherein at least one plate-like blade is providedfor at least either of said first and second rotational shafts.
 13. Adispersing apparatus according to claim 12, wherein a distance from anouter surface of each of said first and second rotational shafts to theouter rotational ends of said stirring blades provided for said firstand second rotational shafts and a distance from the outer rotationalends of said stirring blades to the inner surface of said vessel are notless than three times a mean diameter of said particle media nor morethan ten times.
 14. A dispersing apparatus according to claim 13,wherein rotational directions of said first and second rotational shaftsare the same.
 15. A dispersing apparatus according to claim 12, whereinrotational directions of said first and second rotational shafts are thesame.
 16. A dispersing apparatus comprising:a vessel having ports forsupplying and discharging a material to be dispersed; first and secondrotational shafts disposed in said vessel to run parallel to each otherand rotatively; a plurality of stirring blades provided, in an axialdirection and apart from one another at arbitrary intervals, for saidfirst and second rotational shafts and located alternately in the axialdirection; and particle media arranged to perform a process fordispersing said material and enclosed in said vessel; wherein:portionsof rotational regions of said stirring blades provided for said firstand second rotational shafts overlap, said vessel has an inner surfaceformed by combining two circular arc-curved surfaces formed along outerrotational ends of said stirring blades provided for said first andsecond rotational shafts, said first and second rotational shafts aredisposed horizontally, a horizontal plane includes axes of said firstand second rotational shafts, and a distance from an outer surface ofeach of said first and second rotational shafts to the outer rotationalends of said stirring blades provided for said first and secondrotational shafts and a distance from the outer rotational ends of saidstirring blades to the inner surface of said vessel are not less thenthree times a mean diameter of said particle media nor more than tentimes.
 17. A dispersing apparatus according to claim 16, wherein atleast one plate-like blade is provided for at least either of said firstand second rotational shafts.
 18. A dispersing apparatus according toclaim 17, wherein rotational directions of said first and secondrotational shafts are the same.
 19. A dispersing apparatus comprising:avessel having ports for supplying and discharging a material to bedispersed; first and second rotational shafts disposed in said vessel torun parallel to each other and rotatively; a plurality of stirringblades provided, in an axial direction and apart from one another atarbitrary intervals, for said first and second rotational shafts andlocated alternately in the axial direction; and particle media arrangedto perform a process for dispersing said material and enclosed in saidvessel; wherein:portions of rotational regions of said stirring bladesprovided for said first and second rotational shafts overlap, saidvessel has an inner surface formed by combining two circular arc-curvedsurfaces formed along the outer rotational ends of said stirring bladesprovided for said first and second rotational shafts, said first andsecond rotational shafts are disposed horizontally, a horizontal planeincludes axes of said first and second rotational shafts, and rotationaldirections of said first and second rotational shafts are the same. 20.A dispersing apparatus according to claim 19, wherein at least oneplate-like blade is provided for at least either of said first andsecond rotational shafts.
 21. A dispersing apparatus comprising:a vesselhaving ports for supplying and discharging a material to be dispersed;first and second rotational shafts disposed in said vessel to runparallel to each other and rotatively; a plurality of stirring bladesprovided, in an axial direction and apart from one another at arbitraryintervals, for said first and second rotational shafts and locatedalternately in the axial direction; and particle media arranged toperform a process for dispersing said material and enclosed in saidvessel; wherein:portions of rotational regions of said stirring bladesprovided for said first and second rotational shafts overlap, saidvessel has an inner surface formed by combining two circular arc-curvedsurfaces formed along outer rotational ends of said stirring bladesprovided for said first and second rotational shafts, said first andsecond rotational shafts are disposed horizontally, said shafts can bechanged between a vertical state and a horizontal state, and assumingthat radii of said first and second rotational shafts are rA and rB,rotational radii of each of said stirring blades provided for said firstand second rotational shafts are RA and RB, and a distance between axesof said first and second rotational shafts is L, so that a relationshiprB+RA=rA+RB<L≦0.9 (RA+RB) is satisfied.
 22. A dispersing apparatusaccording to claim 21, wherein at least one plate-like blade is providedfor at least either of said first and second rotational shafts.
 23. Adispersing apparatus according to claim 22, wherein a distance from anouter surface of each of said first and second rotational shafts to theouter rotational ends of said stirring blades provided for said firstand second rotational shafts and a distance from the outer rotationalends of said stirring blades to the inner surface of said vessel are notless than three times a mean diameter of said particle media nor morethan ten times.
 24. A dispersing apparatus according to claim 23,wherein rotational directions of said first and second rotational shaftsare the same.
 25. A dispersing apparatus according to claim 22, whereinrotational directions of said first and second rotational shafts are thesame.
 26. A dispersing apparatus comprising:a vessel having ports forsupplying and discharging a material to be dispersed; first and secondrotational shafts disposed in said vessel to run parallel to each otherand rotatively; a plurality of stirring blades provided, in an axialdirection and apart from one another at arbitrary intervals, for saidfirst and second rotational shafts and located alternately in the axialdirection, and particle media arranged to perform a process fordispersing said material and enclosed in said vessel; wherein:portionsof rotational regions of said stirring blades provided for said firstand second rotational shafts overlap, said vessel has an inner surfaceformed by combining two circular arc-curved surfaces formed along outerrotational ends of said stirring blades provided for said first andsecond rotational shafts, said first and second rotational shafts aredisposed horizontally, said shafts can be changed between a verticalstate and a horizontal state, and a distance from an outer surface ofeach of said first and second rotational shafts to the outer rotationalends of said stirring blades provided for said first and secondrotational shafts and a distance from the outer rotational ends of saidstirring blades to the inner surface of said vessel are not less thenthree times a mean diameter of said particle media nor more than tentimes.
 27. A dispersing apparatus according to claim 26, wherein atleast one plate-like blade is provided for at least either of said firstand second rotational shafts.
 28. A dispersing apparatus according toclaim 27, wherein rotational directions of said first and secondrotational shafts are the same.
 29. A dispersing apparatus comprising:avessel having ports for supplying and discharging a material to bedispersed; first and second rotational shafts disposed in said vessel torun parallel to each other and rotatively; a plurality of stirringblades provided, in an axial direction and apart from one another atarbitrary intervals, for said first and second rotational shafts andlocated alternately in the axial direction; and particle media arrangedto perform a process for dispersing said material and enclosed in saidvessel; wherein:portions of rotational regions of said stirring bladesprovided for said first and second rotational shafts overlap, saidvessel has an inner surface formed by combining two circular arc-curvedsurfaces formed along outer rotational ends of said stirring bladesprovided for said first and second rotational shafts, said first andsecond rotational shafts are disposed horizontally, said shafts can bechanged between a vertical state and a horizontal state, and rotationaldirections of said first and second rotational shafts are the same. 30.A dispersing apparatus according to claim 29, wherein at least oneplate-like blade is provided for at least either of said first andsecond rotational shafts.